Update. We pulled out of the small north facing garden, and then a week later, a huge south facing garden came on the market. Offer accepted. Lots of work to do. Probably not enough money!
See threads re, removing driveway, external wall insulation, building loft conversions, and rear extension ..... aarrgghh!
Now need to start sending money to surveyors ....
I think I found a building surveyor in Essex to use, but if anybody wishes to recommend a local one, now is the time.